Dual-band antenna systems, operating simultaneously at both uplink and downlink frequencies of a multiple beam communication satellite, have the advantage of using half the number of reflectors and half the number of feed horns, when compared with a conventional multiple beam antenna (“MBA”) with a separate set of reflector antennas for each uplink and downlink band. Moreover, such dual-band antenna systems can increase usable space on the spacecraft for other payloads and cost less than conventional MBAs.
Although this type of antenna system is significantly better than conventional MBA systems, the receive (“Rx”) beams suffer from large peak-to-edge gain variations due to an electrically larger reflector size. For example, the reflector is about 50% larger for Rx beams when the reflector is sized for transmit (“Tx”) beams. One approach to compensate for this involves shaping the reflector surface such that it is heavily optimized for Rx frequencies and less optimized for Tx frequencies. Even with this compensation, such a dual-band antenna system suffers from peak-to-edge gain variation of about 5.0 dB to 7.0 dB at the Rx band with 1.0 dB to 2.0 dB gain loss due to pointing error and about 0.5 dB lower gain at the Tx band.
It is therefore considered highly desirable to provide for an antenna system which overcomes the deficiencies discussed above. In particular, it is desirable to provide an improved reflector antenna and to provide a novel MBA system that produces “flat top” Rx beams and more efficient Gaussian transmit beams.